Traditional concepts presently employed today include but are not limited to through air drying (TAD) and conventional machines. An example of a process and machine for making tissue paper using TAD is set forth in U.S. Pat. No. 5,656,132, which is incorporated by reference. The most common methods of drying an uncoated or unsized sheet of paper, including tissue, use cast iron dryer cans or larger structures called “Flying Dutchman” or “Yankee Dryers,” both of which are also cast iron drums. All of these conventional cast iron drums are rotating devices.
Examples of air floatation dryers and their use to dry a variety of substrates are set forth in U.S. Pat. Nos. 3,982,328, 4,218,833 and 5,749,164, each of which is incorporated by reference. Air floatation drying has been used on a paper machine after the paper web has been initially dried. The air floatation drier is arranged after a size press or a precoater, before the coated paper web enters a conventional dryer section composed of conventional cast iron dryer cans to dry the applied coating. The air floatation dryer was used in this manner to prevent the transfer of the wet coating or sizing chemicals to the hot conventional cast iron dryer cans. Air floatation dryers used for this purpose did not have an endless loop to support the wet, coated web in the dryer. Rather, the air cushion in the air floatation dryer would support the wet, coated paper web without contact with another surface. In this manner the surface of the freshly applied coating or chemicals was not damaged.
Pulp and heavy weight paper grades have been dried using an enclosed air dryer. The dryers used in such processes use a transport chain or metal belt that has a very open design that are unsuitable for conveying a wet tissue web and are not capable of the high speeds associated with tissue manufacture.